The present invention relates to a semiconductor laser including an array of a plurality of light emission portions, each of which is particularly adapted to emit laser beams with a multi-mode.
Recently, high output semiconductor lasers have been actively developed. These high output semiconductor lasers are used, for example, as excitation sources of solid lasers, light sources of laser welding, and light sources for communication.
As such high output semiconductor lasers, there are known a broadarea type in which a light emission region is widely formed and an array type in which a plurality of the broad-area type light emission regions are formed for realizing a higher output.
FIG. 8 is a typical sectional view illustrating a configuration of a related art broad-area type array laser. In this semiconductor laser, for example, a cladding layer 11 made from n-type AlGaAs, an active layer 12 made from AlGaAs, and a cladding layer 13 made from p-type AlGaAs are formed on a substrate 10 made from n-type GaAs; and a current block layer 13 is formed on the cladding layer with a pattern in which portions B of the current block layer are spaced from each other with a specific pitch. An n-side electrode M0 is formed overall on the substrate 10 side, and a p-side electrode M is formed overall on the cladding layer 13 side.
When a current is applied between the n-side electrode M0 and the p-side electrode M, the current is concentratedly injected in each gap between two adjacent current block layer portions B, so that a portion of the active layer 12 corresponding to such an area in which the current has been injected becomes a light emission portion LD. The width of each of the light emission portions LD is determined by the width of the gap between two adjacent current block layer portions B. In the case of a broad-area type array laser, the width of each of the light emission portions LD is set to ten xcexcm or more (for example, several tens xcexcm). In such a broad-area type array laser which includes, for example, several tens of the light emission portions LD, it is possible to obtain a laser beam output of several tens watts in total.
The above-described semiconductor laser, however, has the following problem: namely, since the semiconductor laser includes a plurality of high output light emission portions, when all of the light emission portions are simultaneously driven, a large amount of heat is generated. Although a heat sink, such as a Peltier device, is provided for suppressing the heat generation of the light emission portions, the heat sink is not sufficient to prevent the light emission portions from being thermally deteriorated. In particular, if part of the light emission portions is deteriorated, not only is the quantity of light reduced as a whole, but also if the current injection is continued, the amount of heat generated is increased, thus exert in an adverse effect on the other light emission portions.
An object of the present invention is to provide a board-area type, array-semiconductor laser capable of keeping the entire quantity of laser beams constant.
To achieve the above object, according to an aspect of the present invention, there is provided a semiconductor laser including a plurality of light emission portions provided on the same substrate, each of which is adapted to emit laser beams with a multi-mode, wherein part of the plurality of light emission portions constitutes a main light emission group and the rest of the plurality of light emission portions constitute a sub-light emission group, a main electrode for supplying a current to the main light emission group and a sub-electrode for supplying a current to the sub-light emission group are separately provided.
With this configuration, since the plurality of light emission portions, each of which is adapted to emit laser beams with a multi-mode, is divided into the main light emission group and the sub-light emission group, a current can be supplied to the main light emission group via the main electrode, a current can be supplied to the sub-light emission group via the sub-electrode. As a result, in a normal state, a current may be supplied to the main light emission group via the main electrode, and laser beams emitted from the light emission portions constituting the main light emission group are used, and if the output of laser beams emitted from the main light emission group is reduced for some reason, a current may be supplied to the sub-light emission group via the sub-electrode to obtain a desired output of laser beams from the light emission portions constituting the sub-light emission group.